1. Field of the Invention
This invention relates to a method for rinsing single crystal wafers such as of silicon or compound semiconductors and an apparatus for rinsing the wafers. More particularly, this invention relates to a method and an apparatus for washing with purified water silicon wafers which have been washed or etched with a chemical liquid thereby removing from the surfaces of the silicon wafers the chemical liquid still remaining thereon.
2. Description of the Prior Art
Heretofore, in the process for the production of single crystal wafers of silicon, for example, the silicon wafers (hereinafter occasionally referred to briefly as "wafers") which have been washed or etched with such a chemical liquid as an alkali solution or an acid solution were immediately rinsed with purified water without being preparatorily dried by draining.
As an example of method of rinse, there is a multistage manual shaking rinse method. This method will be described below. A plurality of rinsing tanks 41 each provided in the upper part thereof with an overflow discharge part 42 for spent rinsing liquid and in the inner lower part thereof with spouting nozzles 43 for spouting purified water upward are arranged as shown in FIG. 3. A plurality of wafers W after being treated with a chemical liquid are stowed parallelly as suitably spaced in a basket 51 held in place by a retaining member 35 and purified water is fed upward through the spouting nozzles 43. In each rinsing tanks 41 filled with purified water, the basket 51 is manually shaken in a vertical direction. The rinsing action given as described above to the basket 51 is sequentially performed in the plurality of rinsing tanks. The whole operation just described constitutes the multistage manual shaking rinse method. The rinsing tank 41 shown in FIG. 3 is provided therein with an ultrasonic oscillator 3.
In this rinse method, since the purified water is not fed amply to wafers retaining groove parts (not shown ) in the basket 51, the purified water in these groove parts is not sufficiently displaced with fresh supply and the chemical liquid removed from the wafers W is not quickly discharged out of the rinsing tank 41 but is suffered to mingle with the purified water and stagnate inside the rinsing tank 41, with the result that the chemical liquid will tend to persist on the surfaces of the wafers W. The rinse method under consideration, therefore, has the problem that the surfaces of the wafers W which have undergone the multistage rinse are blemished (as by surface roughness, protrusions, and pits presumably caused by the etching reaction of the chemical liquid) and consequently made to assume an bad appearance. This method, therefore, is at a disadvantage in requiring to increase the number of rinsing tanks 41 for use in the multistage operation in order to ensure perfect rinse and inevitably turning the rinsing operation into a troublesome and time-consuming work.